An ultrasound based non-invasive method for the measurement of intrinsic foot kinematics during gait

doi:10.1016/j.jbiomech.2013.12.014

Journal of Biomechanics

Volume 47, Issue 5, 21 March 2014, Pages 1225-1228

https://doi.org/10.1016/j.jbiomech.2013.12.014 Get rights and content

Abstract

Soft tissue artefact (STA) and marker placement variability are sources of error when measuring the intrinsic kinematics of the foot. This study aims to demonstrate a non-invasive, combined ultrasound and motion capture (US/MC) technique to directly measure foot skeletal motion. The novel approach is compared to a standard motion capture protocol. Fourteen participants underwent instrumented barefoot analysis of foot motion during gait. Markers were attached to foot allowing medial longitudinal arch angle and navicular height to be determined. For the US/MC technique, the navicular marker was replaced by an ultrasound transducer which was secured to the foot allowing the skeletal landmark to be imaged. Ultrasound cineloops showing the location of the navicular tuberosity during the walking trials were synchronised with motion capture measurements and markers mounted on the probe allowed the true position of the bony landmark to be determined throughout stance phase. Two discrete variables, minimum navicular height and maximum MLA angle, were compared between the standard and US/MC protocols. Significant differences between minimum navicular height (P=0.004, 95% CI (1.57, 6.54)) and maximum medial longitudinal arch angle (P=0.0034, 95% CI (13.8, 3.4)) were found between the measurement methods. The individual effects of STA and marker placement error were also assessed. US/MC is a non-invasive technique which may help to provide more accurate measurements of intrinsic foot kinematics.

Introduction

The intrinsic kinematics of the foot are of interest for a number of clinical conditions, and this has been reflected in the large number of multi-segment foot models for motion analysis reported in the literature over the past two decades (Bishop et al., 2012). These models tend to be based on skin mounted marker sets, however studies using bone pins have demonstrated significant differences between the true motion of the foot bones and the motion measured using skin mounted markers (Nester et al., 2007). This error is due in part to movement of the surrounding soft tissue relative to the underlying bony landmarks. In addition, the accuracy of marker placement over the chosen landmark has also been shown to be a potential source of error when measuring foot kinematics (Telfer et al., 2010).

There are primarily two reported methods that allow the direct measurement of bone positions when assessing the intrinsic motion of the foot during dynamic activity: bone pins (Nester, 2009) and fluoroscopy (Shultz et al., 2011). These methods however require invasive surgery or exposure of the patient to ionising radiation respectively, potentially limiting their utility for clinical and large scale research applications.

The aim of this study is to demonstrate a non-invasive method which combines ultrasound and motion capture (US/MC) to directly measure skeletal motion during gait and therefore negate STA and marker placement error when measuring selected foot kinematic parameters, and to compare this method to measurements made using a standard protocol with skin mounted markers.

Section snippets

Participants

Fourteen healthy participants, 7♀, age 37.9 years (SD 12.4), height 1.74 m (SD 0.08) and weight 75 kg (SD 11.3) gave informed, written consent to participate in this study. Ethical approval was obtained from the institutional review board prior to the study commencing (reference HLS12/43).

Equipment

Using sampling frequencies of 120 Hz, an 8 camera motion capture system (Opus 3; Qualisys, Gothenburg, Sweden) was used to track retroreflective markers and a force plate embedded in the walkway (Type 9286B;

Results

Motion/time curves for MLA angle and navicular height determined using the two methods are presented in Fig. 3. Significant differences were found between minimum navicular height determined via the two methods, with the standard protocol estimating the height to be 49.1 mm compared to 45.1 mm for the US/MC technique (P=0.004, 95% CI (1.57, 6.54)). Maximum MLA during stance was significantly different between methods (P=0.0034, 95% CI (13.8, 3.4)) with the standard protocol estimating this angle

Discussion

In comparison to the more proximal joints in the lower limb, the relative motion between the bones of the foot is small even in the primary plan of movement. Therefore the impact of STA and other sources of error in motion analysis of the foot is an important issue, with inaccurate measurements potentially clouding the identification of clinically relevant changes to kinematic variables. In particular, the NT landmark is used in a number of multi-segment foot models (Carson et al., 2001, Hyslop

Conflict of interest statement

The authors declare that they have no conflict of interest relating to the material presented in this article.

Acknowledgements

This work was funded in part through the European Commission Framework Seven Programme (Grant number NMP2-SE-2009–228893) as part of the A-FOOTPRINT project (www.afootprint.eu). The funders had no input into the study design, collection, analysis and interpretation of data; the writing of the manuscript; or the decision to submit for publication.

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Short communicationAn ultrasound based non-invasive method for the measurement of intrinsic foot kinematics during gait

Abstract

Introduction

Section snippets

Participants

Equipment

Results

Discussion

Conflict of interest statement

Acknowledgements

J. Biomech.

J. Biomech.

Gait Posture

Gait Posture

J. Biomech.

Short communication
An ultrasound based non-invasive method for the measurement of intrinsic foot kinematics during gait